1. Field of the Invention
This invention relates to apparatus for cleaning teeth, and more particularly to an improved dental cleaning system for removal of tenacious stain and heavy plaque from exposed tooth surfaces by simultaneously directing a stream of air containing entrained cleaning powder and a stream of water onto the surface to be cleaned.
2. Description of the Prior Art
While an effective home care program including regular brushing and flossing is considered essential to dental hygiene, such home care normally cannot be completely effective in removing stain and plaque particularly from relatively inaccessible surfaces between the teeth and from pits and fissures. Accordingly, it is normally recommended that a dental care program include periodic professional cleaning. Such professional cleaning conventionally has involved the removal of calculus, particularly from subgingival surfaces, and the cleaning of exposed enamel surfaces for the removal of stain and plaque by polishing the enamel surface with a rubber cup and an abrasive material, typically pumice, in a paste. This method is effective in cleaning accessible surfaces, but cannot remove all stains from deep pits and fissures.
It has also been known, for example from U.S. Pat. Nos. 3,882,638 and 3,972,123, to employ air abrasive equipment for cleaning teeth, using insoluble abrasive particles entrained in an air stream directed onto the tooth surface while simultaneously discharging a water stream onto the surface. Soluble abrasive cleaning particles or pellets, and powdered abrasive cleaning material, respectively, are disclosed in U.S. Pat. Nos. 4,214,871 and 4,174,571.
The prior art abrasive cleaning devices which have been most widely used commercially employ water delivered in one or more streams adjacent to or surrounding the air abrasive stream to provide a wet surface for more effective cleaning, to eliminate dust from within the patient's mouth, and to dissolve and flush abrasive material from the tooth surface for removal by conventional suction equipment. Although insoluble abrasives have met with only limited acceptance, soluble abrasive material is widely used for professional cleaning of teeth. In particular, sodium bicarbonate abrasive cleaning powder (hereinafter cleaning powder) has been widely accepted and is very effective in removing stain and plaque even from deep pits and fissures.
Difficulty has been encountered in reliably delivering both soluble and insoluble cleaning abrasive materials at a uniform, accurately controllable rate. Dispensing and conveying solid cleaning materials through complex conduit and valving systems by pressurized air has presented difficulty, particularly since it has generally been necessary to vary air pressure and/or flow rate in order to control and vary the amount of abrasive cleaning material delivered to the handpiece. Filters used in the air system generally have been of the disposable type which could not be serviced or cleaned and which if not changed at proper intervals, could result in further difficulty in controlling flow rates and pressures. Similarly, pinch valves used to stop flow through flexible tubing of the system have not always been reliable and have presented substantial difficulty in operation.
The prior art systems of this general type generally have included a separate, valve controlled bleed-off system for depressurizing the cleaning powder supply and dispensing apparatus and the pressurized powder dispensing conduit upon shut-down of the system. Such bleed-off systems required separate filter mechanism for removing and collecting cleaning powder bled from the system to prevent it from being discharged into the open atmosphere. Such filtered bleed-off systems also presented additional service requirements, and sudden bleed-off of air from the pressurized supply container could result in substantial volumes of cleaning material being carried away and wasted.